Recently, it has been proposed that the superlattice structure reduces the lattice thermal conductivity perpendicular to superlattice interface, leading to the improvement of figure of merit of thermoelectric device. We developed a new method of thermal diffusivity measurement in order to prove the above mentioned effect of superlattice. We also applied photoacoustic method for evaluating thermophysical properties of thermoelectric materials.

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Mutual diffusion coefficients for 2-ethylhexylmethacrylate+ketone(acetone, methyl ethyl ketone, methyl propyl ketone)systems were measured at 40°C and 50°C and 0.01-0.19mass% of solvent concentration by using the sorption apparatus with a quartz spring, and were predicted by the free volume theory. For all systems, the mutual diffulsion coefficients obtained depended on the concentration of solvent and increased with the concentration. The parameters required in the prediction model were estimated by applying a previous method based on the physical properties of solvent. The predicted results are in good agreement with the experimental data at an average error within 10%.

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